Modern satellite communication systems provide a robust and reliable infrastructure to distribute voice, data, and video signals for global exchange and broadcast of information. These satellite communication systems have emerged as a viable option to terrestrial communication systems for carrying data traffic such as Internet traffic. A typical satellite Internet system comprises subscriber terminals, a satellite, a ground station, and connectivity to the internet. Communication in such a system occurs along two links: 1) an uplink (or inroute) from a subscriber terminal to the satellite to the ground station to the gateway to the internet; and 2) a downlink (or outroute) from the internet to the gateway to the ground station to the satellite to the subscriber terminal.
During initial installation of a satellite terminal, a ranging process is performed. During ranging, the terminal transmits a signal across available inroute (uplink) frequency channels for a given transmit symbol rate, and receives signal to interference-plus-noise ratio (SINR) measurements for each transmission from a satellite gateway. The terminal also receives a signal for its assigned outroute (downlink) frequency channel, and determines the SINR of the outroute channel. The SINR is determined by the ratio of the signal power divided by the combination of the thermal noise power and the power level of other sources of interference. The ranging process is repeated for each available transmit symbol rate in the network. Based on this ranging process, the terminal determines a baseline for transmission rates it may operate at (channels it may operate on), and correspondingly, the appropriate baseline power setting to use at each rate. The outroute SINR is also stored as part of the ranging process.
Multiple problems may arise following the installation of a satellite terminal. First a satellite terminal installation may occur during poor weather (e.g., rain or snow). Establishing baseline transmission rates in poor weather may limit the possible transmit rates the satellite terminal is capable of operating on during clear sky conditions. Second, the transmit performance of the terminal may degrade over time following a poor mechanical installation of the terminal antenna system. In such an installation, the antenna of the terminal may misalign over time, thereby leading to reductions in the terminal's transmit rates and incorrect baseline power settings for the terminal. Further, still, seasonal changes may cause “drifting” in the transmit characteristics determined during initial installation. For example, tree leaf growth and loss may change the transmit rates and power settings required by a satellite terminal.
Accordingly, it is important for a terminal to redo the ranging process to reestablish the transmit settings when these problems arise. Additionally, it is important to determine which terminals were poorly installed.
The conventional process of addressing these problems relies on a manual determination of whether ranging is needed. In this manual process, satellite network personnel manually examine transmit statistics of each terminal over tens of thousands of terminals. Based on this examination, it is determined if a significant sustained change has occurred in the satellite terminal's transmit performance. If a change has occurred, the ranging process is manually initiated by issuing a ranging command to the terminal from a satellite gateway. Accordingly, the conventional process is a cumbersome and manual-labor intensive process that cannot reliably and dynamically identify the terminals that need ranging.